Feline Infectious Peritonitis

Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is caused by a virus and can affect many of the body systems in cats. It can occur in cats of all ages, but mostly infects cats under the age of 3 years old or over the age of 14 years old. Feline infectious peritonitis typically gets worse over time and often results in death.

The virus acts by damaging the capillary blood vessels throughout the body, which causes the loss of fluid to the tissues and body spaces. The virus tricks your cat’s immune system into assisting in the spread of the virus throughout the body. This disease typically begins with a primary phase that often produces no signs. Occasionally, there may be fever, eye inflammation, diarrhea, or upper respiratory signs, but these usually only last up to a few weeks. If the disease progresses to the secondary phase, it can progress to either a wet form or dry form. In the wet form of this disease, fluid accumulates in the body spaces, while in the dry form, fluid is not produced. The wet form of the disease progresses very quickly, while the dry form usually allows for a longer life expectancy for your cat.

Signs & Symptoms of FIP

Wet Form Symptoms

  • Loss of appetite
  • Depression
  • Listlessness
  • Bloated belly
  • Labored breathing due to fluid in the chest
  • Fever up to 106℉
  • Dehydration
  • Pale tongue, gums, and nose
  • Vomiting
  • Diarrhea
  • Dark urine or jaundice due to liver failure
  • Sudden death due to fluid in the heart sac

Dry Form Symptoms

  • Lethargy
  • Changes in behavior
  • Paralysis
  • Loss of balance or poor coordination of muscles
  • Increased sensitivity to touch
  • Tremors or convulsions
  • Urinary incontinence
  • Discoloration of eye or irregularities in pupil (in some cases, this is the only symptom)

Causes of FIP

Feline infectious peritonitis is caused by a coronavirus that is spread from cat to cat. Ingestion, inhalation, mutual grooming, and exposure to infected feces are the most common routes of infection. Many cats are infected with a coronavirus without symptoms, but less than one percent develops feline infectious peritonitis. Because infection is dependent on constant contact with an infected cat, it is most prevalent in households with more than one cat.

Diagnosis of FIP

Diagnosis begins with a complete history and a physical exam. There are several different tests used to diagnose FIP. The diagnostic path chosen will depend largely on the symptoms your cat has and the availability of diagnostic tools by your veterinarian. Your veterinarian will most likely do the following:

  • CBC/Chemistry Panel - These blood tests will evaluate various internal organ functions, including the heart, liver, kidneys, pancreas, metabolism, and electrolyte balance. The CBC is a measure of the amount and different kinds of red and white blood cells that are present in the body. In this case, your veterinarian would focus on the kidney and liver values because failure of these organs is common. Enzyme levels may also be evaluated to determine the state of the liver.
  • Exudate Analysis - This involves draining the body cavity of the built-up fluid to determine if your cat has the wet form of feline infectious peritonitis. Your veterinarian will use a needle, usually with an ultrasound machine as a guide, to acquire a sample of the fluid. The fluid will be high in protein and your veterinarian may test it for total protein levels. It is yellow to tan in color, will usually froth if shaken, and may clot after being exposed to air. The fluid will be full of various inflammatory cells if microscopically examined.
  • Organ Biopsy - This involves taking a tissue sample from your cat and looking for changes specific to FIP under a microscope.
  • Radiographs - This may show fluid in the thorax, clouding the view of other organs. 
  • Ultrasound - This may show organs surrounded by fluid or enlarged lymph nodes.

ELISA, immunofluorescence, and other diagnostic tests may be used to determine the presence of a coronavirus, but they cannot differentiate between the coronavirus strains. Because many cats have coronaviruses that are often asymptomatic, these tests are not typically effective in diagnosing FIP. However, these tests may be used to confirm FIP when the veterinarian is trying to differentiate the diagnosis between a coronavirus or another non-coronavirus disease.

Treatment for FIP

There is no cure for this disease and once your cat develops the secondary form, progression is rapid. Usually, all cats with this disease will die, and an infected cat has two months to one year to live. However, recovery has been reported in a few cases. Treatment for this disease involves the following:

  • Keeping your cat in a stress-free environment will help with the symptoms.
  • Appetite stimulants and subcutaneous fluids will help with refusal to eat or drink.
  • Antibiotics may be given to prevent secondary infection due to the suppressed immune system.
  • A corticosteroid or low-dose anti-inflammatory may be administered to help reduce inflammation.
  • Another drug, pentoxifylline, may be administered to treat the damage to your cat’s blood vessels.

Prevention of FIP

Feline infectious peritonitis can be prevented by:

  • Frequent scooping of litter/removal of feces.
  • Isolation of infected cats or new cats being introduced to a home.
  • There is currently one vaccine available, but it appears to only be beneficial to kittens that are not already infected with a coronavirus. It is not routinely used because studies have not yet been able to confirm its effectiveness. Before vaccinating, discuss the FIP vaccine with your veterinarian. 

This disease seems to occur most often in pedigreed cat breeds. The following are the breeds that appear to be predisposed to developing FIP: 

  • Abyssinians
  • Bengals
  • Birmans
  • Himalayans
  • Persians
  • Ragdolls
  • Rex breeds

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